Electric and electro-acoustic musical instruments, such as an electric guitar, an acoustic guitar with a pickup, an electric bass, and microphones rely on electronics, such as amplifiers, to amplify and/or modify their sound. In a setting with multiple musicians, such as a band rehearsal, each musician may have an amplifier, and the band as a whole may have mixers to control and monitor the output of the band as a whole. For instance, products such as the Rolls MX41 mixer or the Mackie 1202 accept multiple input channels, allow manipulation of each input, and generate one audio mix.
Often, it is desirable for a band rehearsal to be conducted “silently;” that is, to feed the band's sound into headphones such that the instruments make minimal acoustic sound. Headphone amplifiers can enable silent rehearsals: these devices accept multiple inputs, combine the inputs into one output signal, and feed the output signal into headphones worn by each musician. However, headphone amplifiers do not allow each musician individual control over the constituent parts of a particular mix of inputs that feeds into his headphones. Rather, a common mix is generated by a separate piece of equipment (a “mixer”) and that same mix is directed into each musician's headphones or other listening device. At most, some headphone amplifiers, manufactured for example by Samson and PreSonus, allow a musician to increase the volume of his own input channel (the “More Me” concept) within his own set of headphones. Even with headphone amplifiers, however, a common mix is still created prior to the headphone amplifier so that a change in the overall mix impacts all listeners; individual modifications to other input channels are not possible with headphone amplifiers and mixers used together.